The present invention relates generally to printing presses and more particularly to a signature delivery device for transporting printed products.
In order to singularize or collate signatures from a continuous web of material, the lead and trail edges of consecutive signatures must be separated. A conventional solution to this problem has been to accelerate signatures after they have been cut from the web so as to create a head-to-tail space in the direction of travel of the signatures. However, acceleration can cause marking or transport problems for the signatures.
U.S. Pat. No. 4,577,789 discloses a device for severing sets of endless forms or the like, in which the sets have three layers separated by separator plates or strips after the sets are severed. The layers can thus be separated.
U.K. Patent No. 1 456 648 discloses an apparatus for handling a web of material in which the web is transversely cut to divide the web into successive stacks of superposed sheets. A system conveys the stacks past a succession of devices so that the end sheet of each stack is conveyed to a receptacle for receiving the particular sheet of each stack.
German Patent Application No. 40 31 587 discloses a collator for collecting signatures having a first transport device having a plurality of signature receptacles open to the outside for receiving signatures. A second transport device has plurality of devices with a rear surface to push a plurality of the signatures off the first transport device onto a conveyor belt, so that blocks are formed. To alter the number of signatures that form a block, the angle of the lower section of the first transport device can be varied by moving roll thus minimizing the vertical spacing of the signatures and increasing the number of signatures pushed off by a single rear surface.
An object of the present invention is to provide for improved signature separation and transport.
The present invention provides a signature transport device comprising: a first transport section for transporting a first signature having a first lead edge and a first trail edge, and for transporting a following second signature having a second lead edge and a second trail edge, the first transport section having a signature exit and defining a transport plane; and a second transport section transporting the first and second signatures so that the second lead edge is offset from the transport plane and so that the second lead edge and the first trail edge are separated in a direction perpendicular to the transport plane.
By creating a separation between the lead and trail edge of consecutive signatures, acceleration of the signatures in the direction of travel can be eliminated. Slipping of the signature relative to the transport device can be avoided, so that marking can be reduced and positional accuracy assured.
Preferably, the first transport section includes a set of tapes.
Preferably, the second transport system includes a first belt and a second belt, the first belt having plurality of first wedge regions having a length greater than the signature length, and the second belt having a plurality of second wedge regions interacting with the first wedge regions to separate the second lead edge from the first trail edge.
The first trail edge may be offset from the transport plane by the same amount as the second lead edge, so that the transport plane defines a centerline for the second transport section. The signatures thus are angled with respect to the centerline.
The first and second belts preferably have a straight transport section.
The signature transport device may further include a collating conveyor with a plurality of pockets. The second transport section preferably is oriented vertically so that the signatures in the second transport section drop into the pockets of the conveyor. Preferably, the pocket angle is the same as that of the angle of the signatures in the second transport section.
The direct interface of the second transport section on the collator eliminates the need for storing the signatures and subsequently delivering them from storage for collation.
The present invention also provides a collator having a plurality of the signature transport devices and a collating conveyor.
The present invention also provides a printing press having a folder for cutting a web of printed material into signatures, and the signature transport device.
The present invention also provides a method for transporting signatures through a transport device comprising transporting a first signature in a signature transport plane of a first transport section of the transport device; transporting a second signature following the first signature in the signature transport plane; and moving a lead edge of the second signature with respect to a trail edge of the second signature in a direction perpendicular to the signature transport plane on a second transport section of the transport device.
As used herein, a signature includes a plurality of sheets or a single sheet.